Polyphenylene ether (hereinafter sometimes abbreviated as PPE) has been utilized for various applications because of its characteristics, i.e., heat resistance and water resistance of that resin and good compatibility with a styrenic resin. In particular, it has been widely used in commercial products requiring both water resistance and heat resistance, such as toilet articles and parts around a bath (for example, a washing toilet table, a sink and a housing of a disposable razor). However, in the environment in which these parts are used, the possibility of contacting with, for example, tonic liquid represented by skin lotion, cream or the like is very high. An organic acid ester much contained therein, for example, an alkyl palmitate, a monofatty acid glyceride, a difatty acid glyceride or an alkyl phthalate, strongly acts on a resin composition having an aromatic ring. Accordingly, it becomes necessary to contrive to improve chemical resistance. Further, as the toilet articles, there are present not only large-sized products, but also many small-sized ones, so that injection moldability (flowability) and moldability relating thereto are also required.
As a procedure for improving chemical resistance of the PPE resin composition, there has been known a method of mixing polyethylene (low density and high density polyethylenes), polypropylene or the like abounding in organic solvent resistance together with a hydrogenated type 3 or type 2 aromatic vinyl-conjugate diene block copolymer (HTR), as described in patent documents 1 to 4. In order to sufficiently exhibit the effect of chemical resistance, it is necessary that substances such as polyethylene abounding in chemical resistance are added in an amount of 10% by weight or more. However, these have no compatibility with PPE, and techniques using the HTR for giving compatibility are introduced in patent documents 1 to 5. However, when high shear stress is applied at the time of injection molding, layer separation (so-called lamellar separation) occurs in a molded article. This phenomenon is particularly remarkable in a molded article small in size in which a site having a thickness of 2 mm or less is present, and especially remarkable in a site having a thickness of 0.5 mm or less. This separation phenomenon significantly lowers the strength of the molded article, and concurrently deteriorates chemical resistance. In particular, no effect is achieved at all for a solvent containing an organic acid ester such as a palmitic acid ester derivative or coconut oil contained in the skin lotion or the like as described above.
Techniques of blending an aromatic vinyl-isoprene block copolymer with polyphenylene ether are disclosed in patent documents 5 to 11. In patent documents 5 and 6, it is disclosed that moldability is improved without deteriorating heat resistance, and the effect of inhibiting vibration (vibration damping effect) is disclosed in patent documents 7 to 11. However, these patent documents are silent on chemical resistance, and chemical resistance to the above-mentioned organic acid ester-containing solvent has not been obtained.
Patent Document 1: JP 2-110147 A
Patent Document 2: U.S. Pat. No. 4,242,263
Patent Document 3: Japanese Patent No. 2,797,001
Patent Document 4: Japanese Patent No. 2,797,015
Patent Document 5: JP 7-304908 A
Patent Document 6: European Patent 789,058
Patent Document 7: JP 11-12457 A
Patent Document 8: JP 11-80535 A
Patent Document 9: JP 11-140298 A
Patent Document 10: JP 2001-139798 A
Patent Document 11: JP 2003-55528 A